Investment patterns and kinship cues in a cooperatively breeding bird

In cooperatively breeding species, ‘helpers’ provide care for other individuals’ offspring. Research into cooperative breeding, which initially asked the deceptively simple question ‘why?’, has continued to provide insights in behavioural ecology thanks to the opportunities for adaptation and coevolution that are generated in these unusual societies. I explore some of these potential adaptations in detail, mainly through studying a population of riflemen Acanthisitta chloris, which are passerine birds endemic to New Zealand. Previous work showed that riflemen are kin-based, facultative cooperative breeders. Most help is provided by adult birds, who have dispersed from their natal territory, but commute short distances to provision at the nests of relatives. Help is associated with enhanced recruitment of related offspring, and thus considered likely to confer indirect fitness benefits. These conclusions are substantiated by my results. Provisioning by helpers is a special case of parental investment, and in Chapter 2 I characterise investment by rifleman carers. I find that sealed-bid and conditional cooperation models are inappropriate to describe investment in riflemen, and discuss possible reasons for this. I also demonstrate the validity of provisioning rate as a measure of food delivery in riflemen. In the following two chapters I test the hypothesis that helping drives adaptive sex allocation in cooperative breeders, first using data from riflemen, and then across 26 bird species. Surprisingly, the hypothesis is not supported in either case. In chapters 5 and 6 I consider how riflemen recognise their relatives in order to direct help to them. I identify candidate vocal and chemical kinship cues and test the responses of provisioning riflemen to olfactory manipulations and call playback. My findings have implications for measuring parental investment in birds; show interesting discrepancies with evolutionary theory, and illustrate opportunities and challenges in sensory ecology. These themes are discussed in the final chapter

Global patterns and drivers of avian extinctions at the species and subspecies level

Birds have long fascinated scientists and travellers, so their distribution and abundance through time have been better documented than those of other organisms. Many bird species are known to have gone extinct, but information on subspecies extinctions has never been synthesised comprehensively. We reviewed the timing, spatial patterns, trends and causes of avian extinctions on a global scale, identifying 279 ultrataxa (141 monotypic species and 138 subspecies of polytypic species) that have gone extinct since 1500. Species extinctions peaked in the early 20th century, then fell until the mid 20th century, and have subsequently accelerated. However, extinctions of ultrataxa peaked in the second half of the 20th century. This trend reflects a consistent decline in the rate of extinctions on islands since the beginning of the 20th century, but an acceleration in the extinction rate on continents. Most losses (78.7% of species and 63.0% of subspecies) occurred on oceanic islands. Geographic foci of extinctions include the Hawaiian Islands (36 taxa), mainland Australia and islands (29 taxa), the Mascarene Islands (27 taxa), New Zealand (22 taxa) and French Polynesia (19 taxa). The major proximate drivers of extinction for both species and subspecies are invasive alien species (58.2% and 50.7% of species and subspecies, respectively), hunting (52.4% and 18.8%) and agriculture, including non-timber crops and livestock farming (14.9% and 31.9%). In general, the distribution and drivers of subspecific extinctions are similar to those for species extinctions. However, our finding that, when subspecies are considered, the extinction rate has accelerated in recent decades is both novel and alarming

Counter culture: causes, extent and solutions of systematic bias in the analysis of behavioural counts

We often quantify the rate at which a behaviour occurs by counting the number of times it occurs within a specific, short observation period. Measuring behaviour in such a way is typically unavoidable but induces error. This error acts to systematically reduce effect sizes, including metrics of particular interest to behavioural and evolutionary ecologists such as R2, repeatability (intra-class correlation, ICC) and heritability. Through introducing a null model, the Poisson process, for modelling the frequency of behaviour, we give a mechanistic explanation of how this problem arises and demonstrate how it makes comparisons between studies and species problematic, because the magnitude of the error depends on how frequently the behaviour has been observed as well as how biologically variable the behaviour is. Importantly, the degree of error is predictable and so can be corrected for. Using the example of parental provisioning rate in birds, we assess the applicability of our null model for modelling the frequency of behaviour. We then survey recent literature and demonstrate that the error is rarely accounted for in current analyses. We highlight the problems that arise from this and provide solutions. We further discuss the biological implications of deviations from our null model, and highlight the new avenues of research that they may provide. Adopting our recommendations into analyses of behavioural counts will improve the accuracy of estimated effect sizes and allow meaningful comparisons to be made between studies

Flexibility but no coordination of visits in provisioning riflemen

Parental care strategies occupy a continuum from fixed investments that are consistent across contexts to flexible behaviour that largely depends on external social and environmental cues. Determining the flexibility of care behaviour is important, as it influences the outcome of investment games between multiple individuals caring for the same brood. We investigated the repeatability of provisioning behaviour and the potential for turn taking among breeders and helpers in a cooperatively breeding bird, the rifleman, Acanthisitta chloris. First, we examined whether nest visit rate is an accurate measure of investment by assessing whether carers consistently bring the same size of food, and whether food size is related to nest visit rate. Our results support the use of visit rate as a valid indicator of parental investment. Next, we calculated the repeatability of visit rate and food size to determine whether these behaviours are fixed individual traits or flexible responses to particular contexts. We found that riflemen were flexible in visit rate, supporting responsive models of care over ‘sealed bids’. Finally, we used runs tests to assess whether individual riflemen alternated visits with other carers, indicative of turn taking. We found little evidence of any such coordination of parental provisioning. We conclude that individual flexibility in parental care appears to arise through factors such as breeding status and brood demand, rather than as a real-time response to social partners

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Data from: Sex allocation patterns across cooperatively breeding birds do not support predictions of the repayment hypothesis

The repayment hypothesis predicts that reproductive females in cooperative breeding systems overproduce the helping sex. Thanks to well-documented examples of this predicted sex ratio bias, repayment has been considered an important driver of variation in sex allocation patterns. Here we test this hypothesis using data on population brood sex ratios and facultative sex allocation from 28 cooperatively breeding bird species. We find that biased sex ratios of helpers do not correlate with production biases in brood sex ratios, contrary to predictions. We also test whether females facultatively produce the helping sex in response to a deficiency of help (i.e., when they have fewer or no helpers). Although this is observed in a few species, it is not a significant trend overall, with a mean effect size close to zero. We conclude that, surprisingly, repayment does not appear to be a widespread influence on sex ratios in cooperatively breeding birds. We discuss possible explanations for our results and encourage further examination of the repayment model

coop brood sr

Brood (mprop_brood) and helper (mprop_help) sex ratios, expressed as proportions of males, from published studies of cooperatively breeding birds. See references from appendices for full references. See manuscript for criteria used to determine data quality (3 = high, 1 = low). See Table A1 for abbreviations used in helper_effects (UK = ?, these species were excluded from restricted analysis; NP species were excluded from all analyses). Created in Microsoft Excel

effect sizes

Effect sizes used in meta-analysis of sex ratio adjustment in response to a lack of helpers in cooperatively breeding birds. Test statistics used to calculate effect size are provided, except where these were taken directly from a previous publication (detailed in technique column). Magnitude of effect given in effect_size; effect_exp includes positive/negative direction relative to prediction (biased production of helpful sex in response to deficiency of help). Variance is given in v and used to calculate weight (1/v) for calculation of weighted mean. Columns containing max and/or min are the same as for effect_exp but with the effect sizes of unknown direction treated as positive or negative respectively. Overall weighted mean and confidence interval reported in the manuscript

Drivers of extinction (including both primary and secondary threats) on oceanic islands (black), continental islands (grey) and continents (white).

<p>“Other” includes: Energy production and mining, Transportation and service corridors, Gathering terrestrial plants, Harvest aquatic resource, Human intrusions and disturbance, Water management/use, Other ecosystem modifications, Introduced genetic material, Pollution and Geological events. Abbreviations: R & C development: Residential and commercial development, CC & severe weather: Climate change and severe weather.</p